Microgradient patterned NiO coating on copper current collector for anode-free lithium metal battery

Abstract An energy-economic, rapid, and integrative CO 2 laser-based photothermal process is demonstrated for slurry-coated nickel oxide (NiO) coating on copper (Cu) foil for use as a current collector (CC) in anode-free Li metal battery (AFLMB) applications. Laser irradiation in rapid scanning mode under ambient atmosphere transforms the dense NiO coating into a porous yet highly adherent microstructure integrated with the metal substrate. The film quality was optimized by varying the laser power and scan rate. For the optimum case, lithium ion transport investigations indicated improved Li + desolvation and faster lithium transport, which is demonstrated by its lower activation barrier (50.13 kJ mol −1 ) than that for bare Cu (60.53 kJ mol −1 ). In addition, the uniform lateral diffusion of lithium onto the NiO-modified CC (NMCC) surface resulted in a significant increase in the exchange current density (1.592 mA cm −2 ) compared to that in the case of bare Cu (0.716 mA cm −2 ). This helped prevent dendrite formation and enhanced the cyclic stability of AFLMB by up to 400 cycles at room temperature and up to 700 cycles at an elevated temperature of 40 °C compared to only 150 cycles for bare Cu. The laser-treated NMCC enables efficient lithiation on its surface, which is demonstrated by a lower nucleation overpotential of 12 mV compared to 39 mV for bare Cu. The optimum case of laser-functionalized NiO-modified Cu CC in a full cell with LiFePO 4 retained 24% higher capacity at the 100th cycle than the uncoated Cu CC.